Reliability and Concurrent Validity of Inter-Rectus Distance and Linea Alba Stiffness in Women With

and Without Diastasis Recti Abdominis

N. Green1, E. Nieuwold1, N. Hills2, L. McLean1,2

1 School of Rehabilitation Sciences, University of Ottawa

2School of Rehabilitation Therapy, Queen’s University

Contact Name: Linda McleanContact Email: Linda.McLean@uottawa.ca

Acknowledgements and Disclosures

• Infrastructure was made available through funds provided by the NSERC RTI program

• Operating funds were received from the University of Ottawa Research Development program

• The authors have no conflicts of interest to disclose.

Background

● Diastasis recti abdominis?

○ Traditionally measured using Inter-rectus

distance (IRD)

● Hypothesis put forward by Lee & Hodges (2016)

o The ability of the linea alba to transmit

forces may have a greater impact on trunk

function than the magnitude of IRD

Shear Wave Elastography (SWE)is an emerging technology that can be used to quantify tissue mechanical properties

Objectives

1. To examine between and within-rater reliability of linea alba stiffness measured using shear wave elastography (SWE)

2. Investigate the relationship between IRD and linea alba stiffness measured under 3 conditions: (a) Rest, (b) Head lift, and (c) Semi-Curl-up

Methods

Analysis

Measurements of IRD

and stiffness taken

offline by 2 MSc

physiotherapy

students blinded to

women’s DRA status

and to each other’s

results

Participants

● Nulliparae

● Parous women who

delivered their most

recent baby

(vaginally or c-

section) at least 1

year prior to

participation

Imaging Procedure

3 B-mode and 3 SWE

ultrasound images

taken in supine at each

of three sites at rest,

on head lift, curl-up

● Recruitment through local recreational facilities and physiotherapy clinics. Written informed consent obtained prior to participation.

LA = Linea Alba

RA = Rectus Abdominis

SC = Subcutaneous fatty layer

RA RALA

SC

Inter-rectus distance Linea alba stiffness

Characteristics Mean St Dev

Age (years) 31.8 8.2

IRD (cm) 2.43 1.52

BMI (kg/m2) 25.04 3.87

Waist:Hip ratio (units) 0.81 0.06

Minutes of moderate to high intensity exercise/week)

143 114

Number of Children

Number of Participants

Parity (units) n=0 11

n=1-3 9

Results

ResultsMeasures (units)

Site and Condition

Mean St Dev

MeanStiffness (kPa)

SBU

Rest 30.49 18.42

HL 33.57 24.59

CU 36.14 29.95

3cm SBU

Rest 27.00 14.76

HL 36.28 27.50

CU 46.87 37.52

5cm SBU

Rest 35.21 17.91

HL 40.97 30.20

CU 50.45 37.00

Measures (units)

Site and Condition

Mean St Dev

PeakStiffness (kPa)

SBU

Rest 51.34 46.43

HL 55.54 51.43

CU 64.86 55.91

3cm SBU

Rest 41.94 29.88

HL 62.21 54.29

CU 79.64 62.16

5cm SBU

Rest 52.59 30.66

HL 65.76 58.79

CU 85.14 61.45

Results – reliabilty

Measure Task ICCs (95% CI)

(mean values)

SEM MCID

IRD (cm) Rest 0.955 (0.929, 0.972) 0.738 2.046

Head lift 0.947 (0.917, 0.967) 0.746 2.069

Curl up 0.944 (0.910, 0.964) 0.628 1.742

Mean Stiffness

(kPa)

Rest 0.981 (0.970, 0.988) 5.664 15.700

Head lift 0.991 (0.986, 0.995) 6.118 16.961

Curl up 0.994 (0.991, 0.996) 6.555 18.169

Measure Task ICCs (95% CI)

(mean values)

SEM MCID

IRD (cm) Rest 0.983 (0.975-0.989) 0.542 1.502

Head lift 0.947 (0.917, 0.967) 0.746 2.069

Curl up 0.944 (0.910, 0.964) 0.628 1.742

Mean stiffness

(kPa)

Rest 0.885 (0.836-0.923) 17.166 47.583

Head lift 0.868 (0.812-0.911) 28.748 79.685

Curl up 0.911 (0.871-0.941) 30.22 83.768

Within-Rater Between-Trial Reliability using single measures recorded at all measurement sites

Between-Rater Reliability using the average of the three

measures taken at all measurment sites

Currier’s Criteria:≤ 0.69 = poor

0.70-0.79 = fair0.80-0.89 = good≥ 0.90 = excellent

Results

Slope= 0.88cm/cm; intercept=0.17cm

p=0.00; r2=94.3%

Results

r = -0.41; slope = -4.97kPa/cm; intercept = 43.7kPa; p < 0.001

r = -0.498; slope = -12.50kPa/cm; intercept = 76.800; p<0.001

Discussion

Objectives:

I. Both IRD and LA stiffness had acceptable reliability, which was highest at the sites above the umbilicus

II. Significant linear elationships exist between IRD and LA stiffness

o As IRD , LA stiffness

?

Discussion● The relationship between LA stiffness and IRD were consistent with

our expectations, but much of the model variance was unexplained. The models explain only approximately 14% of the variance in the data

● Next steps ○ investigating these relationships using non-linear models and in a larger

sample of women○ comparing parous women to nulliparous women ○ comparing women with and without DRA

● Goal - to more fully understand the impact of both parity and DRA on the mechanical properties of the linea alba and on trunk function

Conclusion

● Linea alba stiffness measured using shear wave elastography demonstrates adequate reliability to be used in research and in clinical practice

● Large IRDs appear to be associated with lower linea alba stiffness in women, and this warrants further investigation in order for us to more fully understand the impact of pregnancy on trunk mobility and function in women

Thank you!